A bamboo is a plant which has been deeply associated with a life of Japanese from the ancient times. Now, a bamboo thicket is abnormally growing, and is threatening environment in various districts. For this reason, an attempt has been tried to effectively utilize this bamboo as a bamboo charcoal or the like. That is, a moso bamboo (Phyllostachys heterocycla) grown in Japan which has been cut into about 50 cm in length is heated in a space of a closed kiln for bamboo at a temperature of 800° C. or higher, and is carefully carbonized over a period of time, thereby, a bamboo charcoal of high quality can be obtained.
Thereupon, the bamboo is thermally cracked, and a bamboo charcoal leaves with a burnt smell smoke. The bamboo charcoal can be appropriately utilized not only as a fuel, but also as various absorbents or deodorants, or a construction material which is laid on wall surfaces or floor surfaces. On the other hand, the smoke is a mixture of gas and water steam containing a variety of components released from a bamboo by thermal cracking. When this water steam is cooled and recovered, it is separated into a water-soluble liquid and an oily liquid. Among them, the former is crude bamboo vinegar, and the latter is tar matter.
A main component of the bamboo vinegar is acetic acid, but the components is complicated. That is, when water occupying 80% to 90% of the whole is removed, the largest amount of a component is acetic acid, a content thereof is about 3.7%. In addition, minor components containing about 200 or more kinds of compounds are dissolved in the bamboo vinegar. More particularly, when water is removed, main components are composed of organic acids such as acetic acid, propionic acid, and formic acid, alcohols such as methanol, propanol, and ethanol, phenols such as 2-methoxyphenol (guaiacol), and cresol, and neutral substances such as valeric acid ester, as well as carbonyl compounds and base components.
Like this, in addition to acetic acid, various components which are useful in a living body, such as polyphenols and organic acids are contained in a bamboo vinegar, and medicinal benefits can be expected by taking them.
However, a bamboo vinegar contains a cancerogenic substance such as benzopyrene, and other harmful substances such as cresol, formaldehyde, formic acid, and methanol. Therefore, although a bamboo vinegar is used in the agricultural and horticultural, and civil engineering fields by diluting with water for the purpose of disinfection, antibacterial treatment, smell removal, deodorization, harmful insect repellency, and cell activation, it has not been actually used in food utility. For this reason, effect of a wood vinegar or a bamboo vinegar by oral ingestion, for example, effect on an allergy reaction has not been tested yet. In recent years, there is a tendency that an increasing number of people suffer from allergy year and year, and safe improvement or prevention of allergy is strongly desired.
As a method of removing a harmful substance from a bamboo vinegar, Japanese Patent Unexamined Publication No. 2000-53973 describes a method of heating a bamboo vinegar at 40 to 50° C., removing formaldehyde and acetone under reduced pressure, and distilling and condensing the residual solution at 60° C. or higher to obtain a bamboo vinegar.
In addition, Japanese Patent Unexamined Publication No. 2000-160165 describes that a bamboo vinegar is adjusted to pH 9 to 11, and aerated with a carbonic gas to pH 6.5 to 7 to remove separated hydrophobic tar matter. Then, this is distilled at 60 to 80° C. under reduced pressure to remove harmful components such as methanol, phenols, and cresol, and then the residual solution, which is adjusted to pH 2.5 to 3, distilled at 80 to 100° C. under reduced pressure to obtain bamboo vinegar as a distilled solution containing acetic acid as a main component.
However, it can not be said that removal of cancerogenic substances such as benzopyrene, dibenzanthracene and methylcholanthrene, and other harmful substances such as cresol or the like is sufficient through these methods, and anti-allergy action by oral ingestion has not been known. And, such problem was also similar in a wood vinegar.